Such management can nowadays be automated to a large extent through specific computer tools and remotely controlled earth moving units. The automation calls for an efficient exchange of information at all levels, both on and off the site, and preferably in real-time.
Typically, the information flow is relayed through one or more management points. For instance, three-dimensional site models can be generated and updated at an off-site source and sent as site strategic or operative information to an on-site office serving as a local management centre. In response, the latter derives and manages site operative information and instructions for the automated machinery and man-machine interfaces, and reports back to the off-site source.
FIG. 1 illustrates in block diagram form some possible data exchange points used in the management of a worksite.
The off-site office 2 constitutes the main centre for site strategic and operative information exchange, possibly in conjunction with one or several peripheral departments 3 or sub-contractor off-site offices. This high-level information is exchanged with the worksite via a main on-site office 4, which serves as a centralized relay point. The site may comprise multiple on-site offices, each communicating directly with the off-site office. The on-site office further operates as a management centre for communications, personnel and equipment on the site, with which it exchanges operative information. In the example, the main on-site office exchanges data with:                surveying equipment 6, specifically dedicated to geometrical data acquisition, e.g. total stations, theodolites, laser rangefinders, etc.,        equipment for assessment of geographical information (GIS) 6a as locations of special objects and their properties,        mobile unit positioning devices 8, e.g. GPS (global positioning by satellite) receivers, to determine the instant position of mobile apparatus such as excavators, bulldozers, trucks, cranes, etc.,        mobile unit actuators or servos 10, generally through radio-controlled on-board units which command the machinery, either for its displacement along the worksite (propulsion motors) or for actuating a tool, such as a bucket, pneumatic drill, ram, blade, etc.,        on-board sensors 12, for instance to determine the unit's operating parameters, such as fuel level, engine temperature, totalized operating time, idle time, load time, wear indicators, etc.,        ground-based sensors 14, for instance GPS reference stations or apparatus to determine local temperature, humidity, soil characteristics, etc., and        human operator terminals 16, i.e. man-machine interfaces such as control panels, monitors, etc. which may be carried or fixed.        
At least some of the above devices can exchange data via one or more fixed site sub-offices 18 which form fixed hubs, e.g. allocated to a particular part of the site, or a specific type of data/machinery.
In addition to the above physical system management, the central on-site office 4 also manages some administrative tasks at a local level, for instance regarding personnel, progress reports, scheduling of tasks and resources, contacts with local authorities, sub-contractors, material flow, etc. These tasks are performed with computer programs such as spreadsheets, databases, specific software, etc. which are routinely exchanged and updated with the off-site office 2.
In the context of road construction, there has been proposed an open system for road information support known under the name “Osyris”. The aim of this system is to enable contractors and road owners to create their own knowledge bases and quality assurance systems operative over different stages of the road's production and life cycle.
The Osyris system is built on three main component levels: office, on-board computer, and measurement system. The components are assigned to one of the levels; only the framework components, i.e. the product model an mobile services, reside on all levels, linking them together and hence building the backbone of the system.
While this prior art system goes some way towards rationalizing the data flow, there remains a need to for a communications system which allows fully autonomous communication at all levels, with seamless access to the different communications interfaces.
For instance, it would be an advantage if the different entities 6-16 mentioned above could also be able to communicate among themselves directly using a structured address format to allow for a more natural, decentralized, management of information flow. It would also be of advantage if the same communications protocol could be used for all the communications interfaces.
More generally, there is a need for a communication system that allows the hierarchical data exchange structure to be made as flexible as possible, enabling apparatus to communicate with other apparatus without restriction on their respective levels of hierarchy and also allowing different parties on and off the site to be able to address different items of apparatus using a simple, organized address format.
An example of a prior art communications with a working machine is disclosed in Patents Abstracts of Japan vol. 2003, No. 03, May 5, 2003 & JP 2002 332662. The communications are effected through the IP network, with each working machine being assigned an IP address managed through a server.
An IP address as such does not give a direct indication of a possible hierarchical level of a given machine. Indeed, the numbering system used for creating IP addresses is generally based on a sequence of four decimal numbers separated by a period. The first (left-most) number indicates the network address, while the fourth (right-most) number designates the specific network machine or host. That fourth number is allocated according to availability and is not amenable to expressing specific characteristics of its network machine, such as its chain of dependency, i.e. hierarchical position, with respect to other machines in a chosen hierarchical system.
Accordingly, a human or machine presented with just the IP number of a machine on the site cannot immediately identify the context of that machine.
In the field of vehicle maintenance, patent document U.S. Pat. No. 6,370,454 discloses a system of distributed sensors cooperating with an on-board computing device adapted to communicate over the Internet to a local computing device, such as a personal digital assistant. The Internet is used for accessing remote servers to obtain information e.g. on the performance and service of the vehicle.